In finite samples of ferroelectric liquid crystals with parallel smectic layers inclined with respect to the sample surfaces, the chevron structure usually occurs. For the same surface anchoring conditions, the twisted molecular organization may also appear, but in contrast with the bookshelf layer geometry, the twist is confined either to the upper part of the chevron, with the lower part untwisted or vice versa. Therefore two different director configurations with respect to the chevron interface can be recognized. These different configurations can coexist and they can be mediated by the so called inversion line. In this communication, we describe this inversion line within the simplest approximation of the chiral smectic C* elasticity. The self-energy of the inversion line, together with its core energy estimated on the basis of the Peierls-Nabarro model, gives the energetically more favourable solution from two that are possible. Finally the interaction of the inversion line with 2/pi-twist disinclination (unwinding line) is discussed and used to explain the observed coalescence of parts of these lines in the terms of their mutual interaction.